Resource Efficiency

Stunning resolution

With
a large Ultra HD TV, you almost feel that you are on the playing field,
experiencing the tackles, passes, and goals in a soccer match as if you were
part of the team. But because it is not only the size that matters when people
are choosing a TV, but also the resolution and price, Evonik has developed
iXsenic®, a metal oxide semiconductor technology that improves the resolution of
large screens and also reduces their production costs.

TVs are becoming larger and larger. Screen diagonals of sixty inch and more are
not unusual these days. The number of pixels per inch also increases: Full-HD
displays with more than two million pixels and six million subpixels for the
primary colors red, green, and blue are now standard, and manufacturers are
already working intensively on increasing the number of pixels by factors of
four and even 16. After all, what good is a large TV without sharp images and
brilliant colors? Although smaller than classic flat screens for PCs and
laptops, smartphones and tablets are just as popular. The resolution and
picture quality of these mobile devices is definitely not lagging behind the TV
screens.

Function of semiconductors in thin-film transistors

The
task of thin-film transistors is to fulfill viewers’ high demands and enable
high definition television (HDTV). Modern full HD TVs contain about six million
of them. They control the individual subpixels and refresh several 100 frames
per second, which the human eye perceives as flowing movement. The thin-film
transistors are able to do this only because the electrons move fast enough
through the semiconductor layer that is integrated in the thin-film transistors
and transport the signals. The larger the screen, the faster the electrons have
to be in order to guarantee a high resolution.

This is where the display industry faces major technological challenges. At
large displays with high resolutions, the amorphous silicon that is currently
being used as a semiconductor material is stretched to its limits. This is due
to the material properties: ultimately, the speed at which the thin-film
transistors can be switched depends on the electron mobility in the semiconductor
layer. A large, high-resolution LCD TV needs enormous electron mobility:
between 1 and 10 square centimeters per volt-second. Speeds like this are
generally not possible with amorphous silicon or can be achieved only with
enormous technical effort. The result would be a very large TV with blurred
moving images and streaking effects. Other technologies – experts talk of LTPS
and sputtered IGZO – also offer high-performance semiconductors, but they are
time, cost, and resource intensive to produce, since they require large
equipment and high vacuum.

Crisper image and larger display

This
is where iXsenic® from Evonik comes in and offers display manufacturers an
optimum solution: Instead of semiconductor technologies with high vacuum
processing, this technology uses inorganic metal oxide semiconductor material
that is liquid processable and can be applied with a coating process – without
vacuum. This not only simplifies the production of flat screens, it is also
more costeffective, as this process reduces energy costs and effort for display
manufacturers. Depending on the area of application, the metal oxide
semiconductors can exhibit electron mobilities of more than 10 square
centimeters per volt-second and, under ideal conditions, even up to 20 square
centimeters per volt-second. With these properties, they are perfect for
high-resolution in extremely large format LCD and OLED TVs: with iXsenic®, TV
has no limits.

In collaboration with SCREEN Finetech Solutions Co., Ltd., the market leader of
coating equipment for the display industry, Evonik goes even one step further.
By offering a mature manufacturing technology suite the introduction of the
iXsenic® semiconductor technology will be significantly facilitated.

“In order to offer a complete solution for TFT backplane mass production we
need to work on the whole process design,” says Hirofumi Yoshino, General
Manager at SCREEN FT. “We plan to finalize the optimization for all the
processes which realize the highest performance of iXsenic® by the end of this
year.”